Wyoming Highway 90 is a 3.00-mile (4.8 km) north-south Wyoming State Road located in western Converse County southeast of Glenrock.

Wyoming Highway 90 is a fairly short state highway located south-southeast of Glenrock named Boxelder Road. WYO 90 begins southeast of Glenrock and north of the community of Boxelder, for which the roadway is named and provides travel to. Highway 90 picks up where Converse County Route 17 leaves off as the roadway begins south-southeast of Glenrock (Converse CR 17 continues south to Boxelder). WYO 90 heads north passing under Interstate 25 as there is no interchange but only a grade separation between the two highways. Eight-tenths of a mile after crossing I-25, WYO 90 reaches its northern terminus at I-25 BUS/US 20/US 26/US 87 northwest of Interstate 25 exit 160 at Glenrock.

The entire route is in Converse County.